The Cattle Price Cycle: An Exploration in Simulation

The simulation of commodity prices has been undertaken using a myriad of techniques, with some omitting the cyclical component and others ignoring the presence of inter-temporal relationships expressed as autoregressive errors. This study examines the periodicity of cattle prices and the modeling of the cattle cycle for simulation purposes. The AIC criterion is used to determine lengths of various cycles to be included in a harmonic model, with a chained modeling approach providing the best representation of the cattle cycle.cattle Price cycle, harmonic model, simulation,

Pediatric open long-bone fracture and subsequent deep infection risk: The importance of early hospital care

The purpose of the current study was to identify risk factors for deep infection after an open long-bone fracture in pediatric patients. Systematic billing queries were utilized to identify pediatric patients who presented to a level I trauma center from 1998 to 2019 with open long-bone fractures. There were 303 open long-bone fractures, and 24 (7.9%) of these became infected. Fractures of the tibia/fibula

Adaptive homodyne measurement of optical phase

We present an experimental demonstration of the power of real-time feedback in quantum metrology, confirming a theoretical prediction by Wiseman regarding the superior performance of an adaptive homodyne technique for single-shot measurement of optical phase. For phase measurements performed on weak coherent states with no prior knowledge of the signal phase, we show that the variance of adaptive homodyne estimation approaches closer to the fundamental quantum uncertainty limit than any previously demonstrated technique. Our results underscore the importance of real-time feedback for reaching quantum performance limits in coherent telecommunication, precision measurement and information processing.Comment: RevTex4, color PDF figures (separate files), submitted to PR

Deterministic Dicke state preparation with continuous measurement and control

We characterize the long-time projective behavior of the stochastic master equation describing a continuous, collective spin measurement of an atomic ensemble both analytically and numerically. By adding state based feedback, we show that it is possible to prepare highly entangled Dicke states deterministically.Comment: Additional information is available at http://minty.caltech.edu/Ensemble

The Extended Emission-Line Region of 4C 37.43

We have explored the nature of the extended emission-line region around the z=0.37 quasar 4C 37.43, using extensive ground-based and HST imaging and spectroscopy. The velocity field of the ionized gas shows gradual gradients within components but large jumps between components, with no obvious global organization. The HST [O III] image shows radial linear features on the east side of the QSO that appear to mark the edges of an ionization cone. Concentrating on the bright emission peaks ~4\arcsec$ east of the quasar, we find through modeling that we require at least two density regimes contributing significantly to the observed emission-line spectrum: one with a density of ~2 cm^-3, having essentially unity filling factor, and one with a density of ~500 cm^-3, having a very small (~10^-5) filling factor. Because the temperatures of these two components are similar, they cannot be in pressure equilibrium, and there is no obvious source of confinement for the dense regions. We estimate that the dense regions will dissipate on timescales <~10^4 years and therefore need to be continuously regenerated, most likely by shocks. Because we know that some QSOs, at least, begin their lives in conjunction with merger-driven massive starbursts in their host galaxies, an attractive interpretation is that the extended emission region comprises gas that has been expelled as a result of tidal forces during the merger and is now being shocked by the galactic superwind from the starburst. This picture is supported by the observed distribution of the ionized gas, the presence of velocities ranging up to ~700 km s^{-1}, and the existence of at least two QSOs having similarly luminous and complex extended emission regions that are known to have ultra-luminous IR galaxy hosts with current or recent starbursts.Comment: 22 pages, incl. 7 figures; to be published in The Astrophysical Journal, 572 (June 20, 2002 issue

Chandra detection of the intracluster medium around 3C294 at z=1.786

We present a Chandra observation of the powerful radio galaxy 3C294 showing clear evidence for a surrounding intracluster medium. At a redshift of 1.786 this is the most distant cluster of galaxies yet detected in X-rays. The radio core is detected as a point source, which has a spectrum consistent with a heavily-absorbed power law implying an intrinsic 2-10 keV luminosity of ~10^45 erg/s. A small excess of emission is associated with the southern radio hotspots. The soft, diffuse emission from the intracluster medium is centred on the radio source. It has an hour-glass shape in the N-S direction, extending to radii of at least 100 kpc, well beyond the radio source. The X-ray spectrum of this extended component is fit by a thermal model with temperature ~5 keV, or by gas cooling from above 7 keV at rates of ~400-700 Msolar/yr. The rest-frame 0.3-10 keV luminosity of the cluster is ~4.5x10^44 erg/s. The existence of such a cluster is consistent with a low density universe.Comment: 5 pages, 6 figures, accepted by MNRA

A Quantum Langevin Formulation of Risk-Sensitive Optimal Control

In this paper we formulate a risk-sensitive optimal control problem for continuously monitored open quantum systems modelled by quantum Langevin equations. The optimal controller is expressed in terms of a modified conditional state, which we call a risk-sensitive state, that represents measurement knowledge tempered by the control purpose. One of the two components of the optimal controller is dynamic, a filter that computes the risk-sensitive state. The second component is an optimal control feedback function that is found by solving the dynamic programming equation. The optimal controller can be implemented using classical electronics. The ideas are illustrated using an example of feedback control of a two-level atom

Preliminary Assessment of Nonpoint Source Related Ambient Toxicity in and around Lower Galveston Bay

In 1991 aquaculture researchers at the old SeaArama facility in Galveston believed that mortality they were observing in their larval shrimp cultures was a result of toxicity of ambient water in the Gulf of Mexico. The researchers utilized near-shore Gulf of Mexico water for rearing larval shrimp. They hypothesized that 2-butoxyethanol was the toxic agent, originating from Galveston Bay waters flowing into the Gulf following heavy rainfall. However, data were not available to support this hypothesis. The US Environmental Protection Agency (EPA) and the Texas Natural Resource Conservation Commission (TNRCC) in a combined effort decided to conduct a water quality study to investigate these concerns. The purposes of the study were to assess the potential for ambient toxicity in lower Galveston Bay and the Gulf of Mexico following rainfall events, and to determine the need for additional studies for a more complete assessment. A total of five stations were sampled during three sampling events: (I) November 1992, (II) June 1993 and (III) February 1994. Sampling stations included Galveston Bay near Redfish Reef, Galveston Channel, and near-shore Gulf of Mexico off Galveston Island. Two additional industrialized areas were also sampled, Texas City Ship Channel and Chocolate Bay. An attempt was made to sample following significant rainfall in the Galveston Bay watershed to assess the potential impact of nonpoint source pollution on bay water quality. Ambient surface water samples were collected for chemical analysis of conventional parameters, EPA priority pollutants (heavy metals, VOCs, semi-volatiles, pesticides and PCBS), and chronic toxicity testing with mysids and inland silversides. Overall, chemical water quality was good for all sites. The chemical analysis yielded no violations of state water quality standards. Bis(2-ethylhexyl)phthalate at the Gulf of Mexico station exceeded the EPA criterion for protection of human health in February 1994, although the significance is doubtful as this is a common lab contaminant. In November 1992 dissolved nickel approached the state's chronic water quality standard at Chocolate Bay. Chronic toxicity data for mysids and inland silversides, although limited, did not indicate significant chronic effects to either species. Because this was a screening study data should be considered preliminary. Chemical and toxicity data indicate that aquatic life uses in the open bay areas sampled are not impacted by toxic substances originating from non-point sources. The need for future open bay type nonpoint source surface water studies is considered low. Studies to assess localized and/or episodic effects of urban storm water discharges and industrial and agricultural runoff (e.g., western near-shore areas of Galveston Bay; Chocolate Bayou upstream of the area sampled in this study) would be of greater value

Characterizing the entanglement of symmetric many-particle spin-1/2 systems

Analyzing the properties of entanglement in many-particle spin-1/2 systems is generally difficult because the system's Hilbert space grows exponentially with the number of constituent particles, $N$. Fortunately, it is still possible to investigate many-particle entanglement when the state of the system possesses sufficient symmetry. In this paper, we present a practical method for efficiently computing various bipartite entanglement measures for states in the symmetric subspace and perform these calculations for $N\sim 10^3$. By considering all possible bipartite splits, we construct a picture of the multiscale entanglement in large symmetric systems. In particular, we characterize dynamically generated spin-squeezed states by comparing them to known reference states (e.g., GHZ and Dicke states) and new families of states with near-maximal bipartite entropy. We quantify the trade-off between the degree of entanglement and its robustness to particle loss, emphasizing that substantial entanglement need not be fragile.Comment: Updated version reflects changes made in January 200